A conventional disc brake comprises a so-called caliper often made from two separate parts which are held together by pairs of bolts so as to be of generally U-shape in cross-section. A portion of the brake disc is received between the limbs of the U. The bolts are parallel to the axis of the disc. The interior portion of each of these parts extends arcuately over the segment of the disc and provides a cavity to locate a brake pad and guide the same for relatively small movements parallel to said axis in brake application. This is effected by a hydraulic mechanism comprising a piston and a cylinder, and again the axes of these parts are parallel to the axis of rotation.
One problem which is faced by the designer of racing brakes is the need to provide a large pad area. However, long pads tend to wear more at their leading edges so that they become wedge-shaped in cross-section and this necessitates replacement at more frequent intervals than would otherwise be the case.
The maximum length of the pad, peripherally of the disc, is governed by the spacing between one of the mentioned pairs of bolts, since pads require to be inserted in a radial direction and pass through a clearance between those bolts, or an equivalent dimension if the caliper is one-piece.